Energy consumption, CO2 emissions
and other considerations related to
Battery Electric Vehicles
Abstract
1. Electric vehicles consume less primary energy and substantially less final energy than fossil fuel
vehicles of same weight and performance (excluding driving range).
2. Taking account of the emissions generated by the production of electricity, the refining of oil and the
distribution of energy, electric vehicles generate, with the EU electricity mix, less than half the CO2 of
fossil fuel vehicles of same weight and performances (excluding driving range).
3. In addition, because of their limited range, electric vehicles will mainly be used for daily commuting and
urban traffic. They will therefore generally be smaller and lighter than fossil fuel vehicles and
consequently even cleaner and more fuel-efficient. They will also contribute to a reduction in traffic
and car park congestion.
4. Taking account of the production of electricity and the production and refining of oil, as well as of their
distribution, it appears that the four electric vehicles analysed in this study consume around 1.7
times less primary energy and generate on average, with the EU electricity mix, less than half the
CO2 of a Toyota Prius.
5. Electric vehicles will not require significant increases in electrical infrastructure until their
number reaches 20-25%. However, they will provide electricity producers with financial incentives
towards improving the energy efficiency and CO2 emissions of electricity production.
6. If the use of electric vehicles became commonplace for city driving, the results worldwide would be:
·
·
·
·
To save around 20% of oil production.
To significantly reduce urban pollution.
To eliminate almost all traffic noise.
To reduce traffic and parking congestion.
.o0o.
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Energy consumption and CO2 emissions
generated by Electric Vehicles
Comparison with fossil fuel vehicles
1. Summary and Conclusions
1.1 Electric vehicles consume less energy than fossil fuel vehicles.
If we calculate ‘Tank-to-Wheel’, that is to say only on the vehicle, an electric vehicle consumes
around three times less final energy (= petrol, diesel or electricity) than a fossil fuel vehicle with
the same weight and the same performance (excluding driving range).
However, energy is required to produce fossil fuel and electricity, as well as to distribute them. If
we include this energy, then fossil fuel vehicles consume ‘Well-to-Wheel’ 20 to 80% more
primary energy than electric vehicles of the same weight and performance, excluding driving range
(20% = diesel-lead comparison, 80% = petrol-lithium comparison).
1.2 Electric vehicles generate significantly less CO2 than fossil fuel vehicles.
Electric vehicles do not produce emissions and therefore, on a ‘Tank-to-Wheel’ basis, cause
infinitely less pollution than fossil fuel vehicles.
If we compare ‘Well-to-Wheel’ CO2 emissions generated from the source of the primary energy
(oil well, mine…) to the vehicle, an electric vehicle generates on average, with the EU electricity
mix, less than half the CO2 of a fossil fuel vehicle of the same weight and performance (excluding
driving range).
1.3 Electric vehicles will generally be smaller and lighter and therefore even cleaner and
more fuel-efficient.
In fact, because electric vehicles have a range limited by battery capacity, their use will essentially
be limited to commuting and city-like trips, for daily distances of less than 50-100km. Such trips
represent about 80% of the mileage covered by cars. For this usage, a small light vehicle is clearly
preferable because it is more manoeuvrable in traffic and can be parked easier: it is only for longer
trips that the comfort and luxury of a large car are really advantageous. Smaller and lighter
vehicles are intrinsically less energy consuming and therefore even cleaner and more fuelefficient.
In addition, the small size of electric cars will help reducing congestion on roads and in car parks.
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1.4 The electric cars in production or in the pipeline consume less energy and generate
significantly less CO2 emissions than the cleanest fossil fuel cars.
We compared the Toyota Prius hybrid (one of the cleanest petrol-engined cars on the market) with
four electric cars: the Indian REVAi micro-car (the only electric car available to date in Belgium),
the EV1 marketed by General Motors in 1999, the Dutch QUICC! mini-van (scheduled for end
2009) and the American Tesla Roadster sports car (in initial production phase).
Compared with the Prius, these electric cars consume on average almost 4 times less final energy
(Tank-to-Wheel) and 1.7 times less primary energy (Well-to-Wheel). With the EU electricity mix,
they generate ‘Well-to-Wheel’ less than half the CO2.
1.5 Electric vehicles will have a positive impact overall on electricity production.
Since most users will recharge their electric vehicle at night during off-peak hours,
·
·
·
Electric vehicles will essentially be recharged using the least energy-intensive and CO2emitting fraction of the electricity production.
Overall, BEVs will provide a financial incentive for electricity producers to improve the
efficiency of electricity production and reduce its CO2 emissions.
Little expenditure on electricity infrastructure will be required until the number of BEVs
exceeds 20-25% of the total number of cars.
1.6 The use of electric cars would yield to other major advantages.
Since city-like driving represents around 80% of all car journeys, worldwide use of electric cars for
this type of driving would provide:
·
·
·
·
A saving of around 20% in oil production.
A significant reduction in urban pollution.
The elimination of almost all traffic noise.
A noticeable reduction of traffic and car park congestion.
2. Energy consumption
Electric vehicles consume less primary energy and significantly less final energy than fossil fuel
vehicles of the same weight and performance (excluding driving range).
2.1 ‘Tank-to-Wheel’ energy efficiency
For this purpose, let us compute the nominal Tank-to-Wheel energy efficiency for electric and
fossil fuel vehicles, that is to say, the ratio of the energy transmitted to the wheels divided by the
final energy (petrol, diesel or electricity) input into the car (via its fuel tank or electrical plug) in
standard test conditions.
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·
Fossil fuel vehicle: The Tank-to-Wheel energy efficiency (from the fuel tank to the wheels)
of the best internal combustion vehicles (excluding hybrids) is, in nominal operating
conditions, generally less than 22% for diesel and 18% for petrol.
Note that the nominal figures are computed in rather ideal conditions. They vary a lot with
driving style and traffic conditions and are generally lower in real life. They are notably
quite lower in congested urban traffic, since then the engine operates often at low or high
rotation speeds at which its efficiency is low, and because fuel vehicles consume energy
when idling.
In other words only 22% of the energy contained in diesel and 18% of that contained in
petrol is transmitted to the wheels in ideal conditions – the rest is lost as heat!
·
Electric vehicle: The Tank-to-Wheel energy efficiency (from the electrical plug to the
wheels) is typically 60% (55 to 65%) with lead-acid batteries and 72% (65 to 80%) with
lithium batteries: approximately 85-87% for the charger and 75-85% for the charging and
discharging cycle with lead batteries; approximately 88-90% for the charger and 85-95%
for the charging and discharging cycle with lithium batteries; 96-98% for the electronic
engine management; and 90-95% for the electric motor.
These numbers vary little with driving style and conditions, since electric motors have a
reasonably constant efficiency at most rotation speeds and because electric vehicles
consume no energy when idling.
In other words, typically 60-72% of the electrical energy consumed at the plug is
transmitted to the wheels – and 40 to 28% is lost as heat! These figures are valid in all
driving conditions.
The ‘Tank-to-Wheel’ energy efficiency of electric vehicles is therefore around three times better
than that of the best fossil fuel vehicles (excluding hybrids) in ideal conditions. It is even better if
computed in real-life conditions.
This means that an electric vehicle consumes at least three times less final energy than any
fossil fuel vehicle (excluding hybrids) with the same weight and performance (excluding range).
2.2 ‘Well-to-Wheel’ energy efficiency
The Well-to-Wheel energy efficiency of a vehicle is the ratio between the final energy transmitted
to the wheels divided by the primary energy at the source (oil well, mine…). It is equal to the
Tank-to-Wheel efficiency (as computed above in 2.1), multiplied by the Well-to-Tank efficiency,
which is the efficiency from the source of final energy (oil well, mine…) to its introduction into
the vehicle (fuel tank or electrical plug).
2.2.1 Fossil fuel vehicle
The Well-to-Wheel energy efficiency (from the primary energy source to the vehicle wheels) for
the best performing conventional fossil fuel vehicles (excluding hybrids) is nominally around
15% for petrol and 18% for diesel (and lower in most real traffic conditions):
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·
The Well-to-Tank energy efficiency (from the primary energy source to the fuel tank),
which takes into account the energy consumed by the production, refining and transport of
the fuel, is around 83%.
This means that the production, refining and distribution of a litre of fuel delivered to the
vehicle and fuel tank consume the equivalent of a fifth litre of fuel.
·
The nominal Well-to-Wheel energy efficiency of the best fossil fuel vehicles (excluding
hybrids) is therefore around 15% (= 16% x 83%) for petrol and around 18% (= 22% x 83%)
for diesel.
This means that, in ideal driving conditions, only around 15% (petrol) or 18% (diesel) of
the primary energy is transmitted to the wheels – the rest is lost as heat!
·
These numbers can be significantly lower depending on traffic conditions and driving style,
because engine’s efficiency depends largely on rotation speed and since fuel vehicles
consume energy when idling.
2.2.2 Electric vehicle
The ‘Well-to-Wheel’ energy efficiency (from the primary energy source to the car wheels) of an
electric vehicle is around 22% with lead-acid batteries and around 27% with lithium batteries:
·
The ‘Well-to-Tank’ energy efficiency (from the primary energy source to the electrical
plug), taking into account the energy consumed by the production and distribution of the
electricity, is estimated at around 37%:
o The energy efficiency of electricity production is difficult to estimate, because it
varies widely depending on the type of power plant: approximately 30-40% for
conventional power plants, 50-55% for combined-cycle power plants with
integrated gasification, 50-60% for combined-cycle gas power plants, up to around
90% for combined systems were all the steam is re-utilised. Furthermore, any
comparison is difficult for power plants which do not use fossil fuels (wind turbines,
hydroelectric, nuclear, etc).
A figure of around 40% is however often considered a useful average for this type
of calculation. In other words, only around 40% of the primary energy arriving at
the power plant is converted into electricity – the rest is lost as heat!
o The energy efficiency of electricity distribution is around 92.5% (90 to 95%). This
means that approximately 92.5% of the electricity produced at the power plant
arrives at the consumer – the rest is lost as heat!
o The ‘Well-to-Tank’ energy efficiency is therefore estimated at around 37%
(= 40% x 92.5%). This figure is close to the JRC figure of 35% quoted in annex 1.
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·
Given that the ‘Tank-to-Wheel’ efficiency averages 60 % for electric vehicles with leadacid batteries and 72 % for those with lithium batteries (see 2.1), the average ‘Well-toWheel’ energy efficiency of electric vehicles is therefore:
o around 22% (= 60% x 37%) with lead-acid batteries,
o around 27% (= 72% x 37%) with lithium batteries.
This means that only around 22% (lead-acid) to 26% (lithium) of the primary energy is
transmitted to the car wheels – the rest is lost as heat! These numbers depends little on the driving
style and traffic conditions, since electric motors have a reasonably constant efficiency over most
rotation speeds and because electric vehicles consume no energy when idling.
2.2.3 Comparison
Nominally, the ‘Well-to-Wheel’ energy efficiency:
·
of an electric vehicle with lead-acid batteries is on average:
o 1.2 times better than that of the best diesel vehicles (excluding hybrids).
o 1.5 times better than that of the best petrol vehicles (excluding hybrids).
·
of an electric vehicle with lithium batteries is on average:
o 1.5 times better than the best diesel vehicles (excluding hybrids).
o 1.8 times better than the best petrol vehicles (excluding hybrids).
In real traffic conditions, these ratios can be much higher.
This means that over 20 to 80% more primary energy is required for a fossil fuel vehicle
(excluding hybrids) than for an electric vehicle with the same weight and performance
(excluding driving range).
3. CO2 emissions
Electric vehicles generate significantly less CO2 emissions than fossil fuel vehicles with the same
weight, power and performance (excluding driving range).
3.1 Tank-to-Wheel emissions of CO2
The manufacturers of fossil fuel vehicles only provide figures for the emissions generated directly
by the operation of the car’s engine, in other words of the ‘Tank-to-Wheel’ emissions (from the
petrol tank to the wheels).
For electric vehicles, which emit nothing during their operation, the Tank-to-Wheel CO2 emissions
are zero: electric vehicles are therefore infinitely cleaner than fossil fuel vehicles.
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3.2 Well-to-Wheel emissions of CO2
It is more appropriate to compute Well-to-Wheel CO2 emissions in order to compare electric
vehicles with fossil fuel vehicles, that is to say the CO2 emissions generated not only by the vehicle,
but also by the power plant or the oil refinery and by the distribution of the fuel or electricity.
3.2.1 Petrol-engined vehicle
·
Nominally, for each kWh of energy transmitted to the wheels, around 5.6 kWh (= 1 kWh /
18%) of petrol in the tank is required Tank-to-Wheel (18% = efficiency – see 2.1). This
number is higher in most real traffic conditions.
·
According to appendix 2, the Joint Research Centre of the European Commission estimated
in 2006 that in order to obtain the Well-to-Wheel value for CO2 emissions from a petrolengined vehicle, it is necessary to add 17% to the Tank-to-Wheel figures. Since:
- the combustion energy from petrol is around 37 MJ/l and 1 kWh = 3.6 MJ,
- the combustion of 1 litre of petrol produces around 2.35 kg of CO2,
Therefore Well-to-Wheel, each kWh of energy transmitted to the wheels emits nominally
around 1490 g of CO2 (= 5.6 kWh x 3.6 MJ/kWh / 37 MJ/l x 2.35 kg CO2/l x (1+17%) x
1000 g/kg) – and generally more in real traffic conditions.
3.2.2 Diesel-engined vehicle
·
Nominally, for each kWh of energy transmitted to the wheels, around 4.5 kWh (= 1 kWh /
22%) of fuel is required (22% = Tank-to-Wheel efficiency – see 2.1). This number is
higher in most real traffic conditions.
·
According to appendix 2, in order to obtain the Well-to-Wheel value for CO2 emissions of
a diesel-engined vehicle, it is necessary to add 19% to the Tank-to-Wheel figures. Since:
- the combustion energy of the diesel engine is around 38 MJ/l and 1 kWh = 3.6 MJ,
- the combustion of 1 litre of diesel fuel produces around 2.7 kg of CO2,
Therefore, each kWh of energy transmitted to the wheels emits, Well-to-Wheel, around
1380 g of CO2 (= 4.5 kWh x 3.6 MJ/kWh / 38 MJ/l x 2.7 kg CO2/l x (1+19%) x 1000 g/kg)
– and generally more in real traffic conditions.
3.2.3 Electric vehicle with lead-acid batteries
·
For each kWh of energy transmitted to the wheels, an average of 1.7 kWh of electrical
energy is required Tank-to-Wheel (= 1 kWh / 60% – see calculation in 2.1), whatever the
driving style and traffic conditions.
·
According to the JRC, the production and distribution of one kWh of electricity generates,
with the 2006 average European Union (EU) energy mix, around 443 g of CO2 (see
appendix 1). Therefore Well-to-Wheel, each kWh of energy transmitted to the wheels
generates on average 738 g of CO2 (= 1.7 kWh x 443 g CO2/kWh).
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3.2.4 Electric vehicle with lithium batteries
·
For each kWh of energy transmitted to the wheels, an average of 1.4 kWh of electrical
energy is required (= 1 kWh / 72% – seek calculation in 2.1), whatever the driving style
and traffic conditions.
·
Therefore, with the average EU energy mix, each kWh of energy transmitted to the wheels
generates around 616 g of CO2 Well-to-Wheel (= 1.4 kWh x 290 g CO2/kWh).
3.2.5 Comparison of CO2 emissions
With the average EU electricity mix, Well-to-Wheel CO2 emissions of an electric vehicle are, on
the average, nominally less than half the CO2 emissions of a fossil fuel vehicle with the same
weight and performance (excluding driving range) in nominal traffic conditions – and even less in
most real traffic conditions :
·
·
·
·
CO2 of a diesel powered car = 1.9 x CO2 of an electric car with lead-acid batteries
CO2 of a petrol powered car = 2.0 x CO2 of an electric car with lead-acid batteries
CO2 of a diesel powered car = 2.2 x CO2 of an electric car with lithium batteries
CO2 of a petrol powered car = 2.4 x CO2 of an electric car with lithium batteries
These ratios are generally higher in real traffic conditions.
3.2.6 Remark
The emissions generated by electric vehicles in a country depend on the electricity mix in that
country. For instance:
·
The Belgian electricity mix emitted, in 2003, 290 g CO2/kWh (according to IEA - annex 1).
With this number, Well-to-Wheel CO2 emissions of an electric car in Belgium are more
than three times less than a fossil fuel vehicle with the same weight and performance:
o
o
o
o
CO2 of a diesel powered car = 2.9 x CO2 of an electric car with lead-acid batteries
CO2 of a petrol powered car = 3.1 x CO2 of an electric car with lead-acid batteries
CO2 of a diesel powered car = 3.4 x CO2 of an electric car with lithium batteries
CO2 of a petrol powered car = 3.7 x CO2 of an electric car with lithium batteries
·
If an electric vehicle is recharged mainly with renewable or nuclear electricity, which
generate practically no CO2 emission, its Well-to-Wheel CO2 emission are close to zero.
This is the case in countries such as Norway, Sweden and France.
·
If an electric vehicle is recharged mainly with coal power plants, which generate over
1000 g CO2/kWh, its Well-to-Wheel CO2 emissions are equal to or higher than a fossil
fuel vehicle with the same weight and performance. This is the case in countries such as
Luxemburg and Poland.
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4. Weight and power considerations
Given that electric cars have a limited range due to their battery capacity, their use will essentially
be limited to commuting, town trips and other short trips which are often made in dense traffic
conditions and with a single person on board. Also, it is generally accepted that about 80% of cars
mileage are for trips of less than 50 km with a single person on board.
For this type of traffic, a small light car is clearly preferable because it is manoeuvrable in traffic
and can be parked more easily. It is only for longer journeys that the comfort and luxury of a large
powerful car are really advantageous.
Indeed, most electric cars currently in production or in the pipeline are small and light:
·
Small manufacturers specialised in electric cars (such as REVA, Duracar and Lumeneo)
generally opt for tubular chassis with plastic bodies, which are much lighter than steel
bodies.
·
Several major manufacturers are getting prepared to test the market by converting their
smaller models to electric power (such as SMART, MINI and Mitsubishi iMiev). If
successful, it is not unlikely that they will thereafter design models specifically for electric
propulsion.
·
It must be noted that, although batteries are much heavier than fuel tanks, electric cars can
be made lighter than conventional cars while having a driving range sufficient the daily
trips of most drivers:
o An electric motor is several times lighter than an internal combustion engine with
the same power.
o An electric car does not require a gearbox.
o An electric car does not require the heavy acoustic insulation and the steel body that
are necessary to damp the sound produced by the engine.
o It can be expected that batteries will become increasingly smaller and lighter in the
future, which will further reduce electric vehicles’ weight to range ratio.
It is therefore likely that electric vehicles will tend to become increasingly smaller and lighter.
Obviously, for a same technology, small light cars are more energy-efficient and emit less CO2
than large powerful ones.
Therefore, electric cars will be even more energy efficient and emit even less CO2 than fossil fuel
cars.
Furthermore, their reduced size will also contribute to reducing traffic and parking congestion.
5. Comparison between some vehicles
To illustrate these figures, let us compute the quantity of primary energy consumed by four electric
vehicles and their Well-to-Wheel CO2 emissions in nominal conditions.
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·
The REVAi is a heavy Indian electric micro-quadricycle with 2+2 seating, very
manoeuvrable in town and with a top speed of 80 km/h. In production since 2001, it is
currently the only electric car marketed in Belgium and in many European countries.
·
The EV1 is the two-seater electric coupe that General Motors marketed in the United States
from 1996 to 1999.
·
The QUICC! from Duracar is a small Dutch electric two-seater minivan. It is scheduled to
go on sale in the second half of 2009.
·
The Tesla Roadster is an American two-seater electric sports car based on the Lotus Elise
with performance competing with the best petrol-engined sports cars. Pre-marketing began
this year in the United States.
5.1 Fossil fuel reference vehicle
As a point of comparison, we have chosen the 2008 Toyota Prius, one of the cleanest fossil fuel
vehicles on the market whose nominal petrol consumption is 4.3 litres per 100 km and whose
nominal Tank-to-Wheel emissions are 104 g CO2/km. Therefore:
·
The nominal Tank-to-Wheel energy of the Prius is around 44 kWh/100km
(= 4.3 l/100km x 37 MJ/l / 3.6 MJ/kWh).
This figure must be divided by the Well-to-Tank efficiency in order to obtain the Well-toWheel values (approximately 80% - see 2.2.1). So we have:
·
Nominal Well-to-Wheel consumption: approximately 55 kWh/100km
(= 44 kWh/100km / 80%) of primary energy.
·
Nominal Well-to-Wheel emissions of CO2: approximately 122 g CO2/km
(= 104 g CO2/km x (1 + 17%) (see 3.2.1).
5.2 REVAi electric car
The Indian REVAi is a small electric car that has lead-acid batteries and uses technology
developed ten years ago. The nominal figures provided by the constructor (www.revaindia.com)
are:
· Electricity consumption for each full charge: approx. 9 kWh
· Range on a full charge: 80 km nominal
Therefore:
·
Nominal Tank-to-Wheel consumption: approximately 11 kWh/100 km of electricity
(= 9 kWh/charge / 80 km/charge x 100), or almost 4 times less than the Prius.
·
As for all electric vehicles, Tank-to-Wheel CO2 emissions are zero.
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·
Nominal Well-to-Wheel consumption: approximately 30 kWh/100 km
(= 11 kWh / 37%) of primary energy, or around 1.8 times less than the Prius.
·
Nominal CO2 emissions Well-to-Wheel: approximately 50 g CO2/km
(= 11 kWh/100 km / 100 x 443 g CO2/kWh) with the average EU energy mix, or almost
2.5 times less than the Prius.
5.3 EV1 electric car
The 1999 EV1 model from General Motors used up-to-date technology and efficient NiMH
batteries. According to the US Department of Energy (DOE) (source:
http://www1.eere.energy.gov/vehiclesandfuels/avta/pdfs/fsev/eva_results/ev1_eva.pdf), its
nominal Tank-to-Wheel consumption was around 11 kWh/100 km of electricity
(= 179 Wh/mile / 1.609 km/mile x 100 km/100km), or the same as the REVA.
Therefore, its nominal Well-to-Wheel characteristics are the same as the REVAi: 30 kWh/100 km
of primary energy (approximately 1.8 times less than the Prius) and 50 g CO2/km with the average
EU energy mix (almost 2.5 times less than the Prius).
The EV1 weighed almost twice as much as the REVA and had a much better performance.
It is therefore remarkable that its fuel consumption and CO2 emissions were the same as those of
the REVAi. This may perhaps be explained by greater efficiency of the EV1’s batteries, electronics
and/or motor, as well as by its advanced aerodynamics.
5.4 QUICC! electric mini van
The small Dutch QUICC! electric mini van will use different types of batteries. The manufacturer
has announced an electricity consumption of 1 kWh per 7 km with lead-acid batteries (see
appendix 2). Therefore:
·
Nominal Tank-to-Wheel consumption: approximately 14 kWh/100 km of electricity
(= 1 kWh / 7 km x 100), or about three times less than the Prius.
·
As for all electric vehicles, its CO2 emissions Tank-to-Wheel are zero.
·
Nominal Well-to-Wheel consumption: approximately 39 kWh/100 km
(= 14 kWh / 37%) of primary energy, or around 1.4 times less than the Prius.
·
Nominal CO2 emissions Well-to-Wheel: approximately 63 g CO2/km
(= 11 kWh/100 km / 100 x 443 g CO2/kWh) with the average EU energy mix, or almost
half of the Prius.
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5.5 TESLA electric car
The American Tesla Roadster electric sports car uses lithium batteries with advanced technology.
The manufacturer announces a nominal Tank-to-Wheel efficiency of 2.18 km/MJ (source:
www.teslamotors.com/efficiency/well_to_wheel.php). Based on this efficiency, we find:
·
Nominal Tank-to-Wheel consumption: 12.7 kWh/100 km of electricity
(= 1 / 2.18 km/MJ / 3.6 MJ/kWh x 100), or 3.5 times less than the Prius.
·
As for all electric vehicles, its CO2 emissions Tank-to-Wheel are zero.
·
Nominal Well-to-Wheel consumption: 34.4 kWh/100 km
(= 12.7 kWh / 37%) of primary energy, or approximately 1.6 times less than the Prius.
·
Nominal CO2 emissions Well-to-Wheel: 56 g CO2/km
(= 12.7 kWh/100 km / 100 x 443 g CO2/kWh) with the average EU energy mix,
i.e. 2.2 times less than the Prius.
5.6 Summary
The summary table below shows that, compared to the Prius, electric cars available on the market
or in the pipeline, consume on average 3.6 times less energy Tank-to-Wheel and 1.7 times less
primary energy Well-to-Wheel, and that they generate Well-to-Wheel 2.3 times less CO2 with the
average EU electricity mix.
Prius
Final energy
(Tank-toWheel)
kWh/100km
44
Primary energy
CO2 Emissions
(Well-to-Wheel)
Well-to-Wheel
kWh/100km
55
g CO2/km
122
REVAi
EV1 NiMH 1999
QUICC!
TESLA Roadster
11
11
14
13
30
30
39
34
50
50
63
56
Ratio Prius/electric cars
3.7
1.7
2.3
REMARKS:
·
In this chapter, we have consistently used the nominal figures provided by manufacturers
(for the Prius as well as for the electric cars). As we know, figures computed in real traffic
conditions are generally quite worse and depend also largely on driver’s style. However,
assuming all manufacturers use similar nominal conditions, comparisons remain reasonably
valid in real traffic conditions and with different drivers.
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·
CO2 emissions of electric cars are here computed using JRC’s 2006 EU electricity mix
number (443 g CO2/kWh – see annex 1). This number varies greatly from one member
state to the other. For instance:
Country
Sweden
France
Belgium
EU15
Germany
Netherlands & UK
Denmark
Luxemburg
gCO2/kWh
40
90
290
443
600
640
840
1080
Average CO2
electric cars
5
11
35
54
73
78
102
131
Prius/electric
CO2 ratio
25.0
11.1
3.5
2.3
1.7
1.6
1.2
0.9
6. Impact on electricity production
Electric vehicles will improve the efficiency and cleanliness of electricity production without
requiring, in a first stage, any significant increase in infrastructure
Electric vehicle will consume a lot of electricity - approximately 2000 kWh/year for a car whereas the average consumption of Belgian households is around 3500 kWh/year. In order to
make savings, the majority of users will prefer to recharge their electric vehicle at night during off
peak-hours, in order to benefit from the cheapest tariff. For electricity production this offers
several advantages:
·
For continuous electricity production, it is generally more profitable to operate highefficiency power plants which cause less CO2 emissions and air pollution, since their
marginal operating cost is lower and their higher investment expenditure can be depreciated
over more operating hours.
Conversely, in order to supply the additional electricity during short periods of high
demand, it is generally more profitable to operate less capital-intensive power plants, which
have a lower efficiency and generate more CO2 emissions and air pollution, because their
lower investment expenditure can only be depreciated over a small number of operating
hours.
Therefore, electric vehicles being essentially charged with off-peak electricity, BEVs will
use the most efficient and less CO2 emitting fraction of the electricity production: this
will further improve BEVs Well-to-Wheel energy consumption and CO2 emissions.
·
The increase in electricity consumption during off-peak hours will contribute towards a
levelling of the electricity demand. This will provide electricity producers with a financial
incentive to profitably replace low-capital peak power plants, which are less efficient and
emit more CO2, with capital-intensive power plants designed for continuous operation,
which are more efficient and emit less CO2 and air pollutants. This will overall improve
the efficiency and CO2 emissions of the electricity production.
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·
Electric vehicles will require little capital expenditure on electrical infrastructure
(network and power plants) in the first stages of BEV commercialisation. Indeed,
infrastructure is dimensioned to cope with the periods of high demand during which few
electric vehicles will be on charge in order to benefit of off-peak tariffs. This will
increasingly be the case with the generalisation of smart electricity metering which will
provide strong incentives to charge off-peak.
In appendix 3, we compute that at least 23% of the cars in France can be electric cars
without requiring significant increase in the electrical infrastructure, assuming that all
BEVs are charged off peak hours. It is likely that this number can be roughly extrapolated
to the whole of Europe.
7. Other factors to be taken into consideration
7.1 Electric vehicles reduce oil dependency
Only a small fraction of electrical energy is generated using petroleum products. Furthermore,
urban-like traffic (trips of less than 50km) represents worldwide around 75 to 80% of cars mileage
and consumes around 20% of the total petroleum production.
Hence, worldwide oil consumption would diminish by around 20% if all these trips were made in
electric vehicles. This would significantly reduce our dependency on oil.
7.2 Electric vehicles reduce urban pollution
A large proportion of the pollutants emitted in town are produced by road traffic. For example, the
MIRA-T report estimates that for Flanders, road traffic is responsible for 49% of NOx emissions,
32% of carbon monoxide (CO), 17% of hydrocarbons, and 25% of fine particles (PM10). Since
electricity production only emits a fraction of these pollutants, the generalised use of electric
vehicles in cities would significantly reduce urban pollution.
7.3 Electric vehicles reduce urban noise
Road traffic is responsible for the majority of the noise in cities. Since electric vehicles are very
silent, widespread use in town would eliminate the majority of the road noise, thus significantly
reducing urban noise levels.
NOTE: It is incorrect that the lack of noise is dangerous for pedestrians and other road users:
· Pedestrians look left and right before crossing – they do not close their eyes and listen to
the sound!
· Bicycles are even more silent than BEVs and are not known to be a hazard to pedestrians
(except of footpaths).
· Blind people generally have an excellent hearing and can hear the tire and wind noise
produced by BEVs. Furthermore, they are usually precautious when crossing streets.
Anybody driving a BEV can confirm it. And statistics do not show that BEVs cause more
accidents.
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6.4 Electric cars reduce traffic and parking congestion
Being generally smaller that average fossil fuel cars, electric cars take less space in road traffic and
will therefore somewhat reduce traffic congestion.
Also in some countries, smaller parking spaces are already reserved for ultra-small cars such as the
SMART. With the multiplication of ultra-small electric cars, it is likely that more small parking
places will be made available, providing more parking places per unit of surface. This will
contribute to reduce car parks’ congestion.
.o0o.
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Appendix 1:
National average values for CO2 emissions per electrical kWh for various countries
Source 1: IEA
IEA 2003 report, retrieved from
http://www.econologie.com/europe-emissions-de-co2-par-pays-etpar-kwh-electrique-articles-3722.html.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Sweden: 0.04 kg CO2 / kWh electricity
France: 0.09 kg CO2 / kWh electricity
Austria: 0.20 kg CO2 / kWh electricity
Finland: 0.24 kg CO2 / kWh electricity
Belgium: 0.29 kg CO2 / kWh electricity
Spain: 0.48 kg CO2 / kWh electricity
Italy: 0.59 kg CO2 / kWh electricity
Germany: 0.60 kg CO2 / kWh electricity
Netherlands: 0.64 kg CO2 / kWh electricity
Greece: 0.64 kg CO2 / kWh electricity
United Kingdom: 0.64 kg CO2/ kWh electricity
Portugal: 0.64 kg CO2 / kWh electricity
Ireland: 0.70 kg CO2 / kWh electricity
Denmark: 0.84 kg CO2 / kWh electricity
Luxembourg: 1.08 kg CO2 / kWh electricity
Average for EU15: 0.46 kg CO2 / kWh electricity
Source 2: JRC
The 2006 “Well-to-Tank” report of the Joint Research Centre (JRC) of the European Commission
quotes a EU WTT figure of 430 g CO2/kWh – see
http://ies.jrc.ec.europa.eu/uploads/media/WTT_Report_010307.pdf page 51):
“Including the distribution losses to the medium voltage level the overall energy efficiency is around 35 %
and the corresponding GHG emissions 430 g CO2eq/kWhe (119 g CO2eq/MJe). A further correction is made
for those cases where electricity is produced or used at low voltage. The detailed primary energy composition
is given in WTT Appendix 1, section 3.”
Assuming a medium to low voltage loss of 3%, EU electricity’s CO2 emissions are 443 g
CO2/kWh.
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Appendix 2: Proving EVs to be the most environmentally friendly!
Source: DuraCar Holding B.V.
In 2005 there were 790 million cars worldwide. At least 14% of worldwide greenhouse gas emissions are
from transport. Looking at the calculations on the next page, it is important to distinguish between: Wellto-Wheel = Well-to-Tank + Tank-to-Wheel.
According to the ANWB , the Dutch equivalent of the ‘RAC Patrol motoring organization’, the two cars
that are perceived as being most environmental friendly are 2 passenger cars, Toyota Prius and Honda
Civic. Obviously this is not a coincidence.
The issue with published grams of CO2 per km figures is that these are always tank-to-wheel numbers.
German electric mobility expert, Mr. Tomi Engel, conducted an extended research for DGS (Deutsche
Gesellschaft für Sonnenenergie e.V. – www.dgs.de) and BSM (Bundesverband Solare Mobilität – www.solarmobil.net) and
published results in a book (ISBN 978-3-89963-327-7). All the numbers below can also be found in his
publication.
In order to include the CO2 that originates from the production of petrol or diesel, the following factors have
to be taken into account (source: EJRC-2006, European Commission Joint Research Centre):
Petrol
Diesel
Natural Gas
17%
19%
15%
Most EV producers or start-ups publish zero grams of CO2 per km. However, this is tank-to-wheel as well.
The German öko-institute GEMIS, published studies about the energy sector and amounts of CO2
originating from different types of electricity production. These numbers provide the necessary Well-totank numbers in order to provide a complete overview.
EU 15 Gridmix
Solar Energy
Wind Energy
439 g CO2/kWh
89-168 g CO2/kWh
19 g CO2/kWh
439 / 7 = 63 g CO2/km
89-168 / 7 = 12 – 24 g CO2/km
19 / 7 = 3 g CO2/km
QUICC! uses 1kWh per 7 kilometers (tested and calculated together with Prof. Sauer, battery specialist,
from the RWTH – technical university of Aachen, Germany).
This would result in the following results, proving in a complete Well-to-Wheel analysis that driving EVs is
by far the most environmental option!
Car
Most popular hybrid passenger
car
2nd most popular hybrid
passenger car
Most popular delivery van
2nd most popular delivery van
QUICC!
QUICC!
QUICC!
Type of
Energy
HEV
Published
Tank-to-Wheel
CO2 g / km
104 g/km
Well-to-Tank
CO2 g/km
+17%
Total
Well-to-Wheel CO2 g /
km
122 g/km
HEV
109 g/km
+17%
128 g/km
Diesel
Diesel
Wind
energy
Solar
energy
EU15
gridmix
161 g/km
147 g/km
0 g/km
+19%
+19%
3 g /km
192 g/km
175 g/km
3 g /km
0 g/km
12 – 24 g/km
12 – 24 g/km
0 g/km
63 g/km
63 g/km
In this comparison the delivery vans chosen have engines of approx. 1.4 litres.
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Appendix 3: Electrical infrastructure
In this annex, we provide a bold-part answer to the following question is: How many battery
electric vehicles (BEVs) can be put on the road without requiring additional electrical
infrastructure (grid and/or power plants)?
Electricity demand varies greatly:
· During the day: it is lowest at night, higher in the day and generally peaks in the evening
· During the week: it is lowest during week-ends.
· During the year: in temperate European countries, it is higher in the winter
Thus electricity demand is highest during winter’s weekday evenings (around 6-7pm). Electricity
production and transport infrastructure is designed to cope with these peaks. BEVs will require
additional infrastructure only if they cause an electrical consumption increase during peak hours.
Therefore, our question can be rephrased as: How many BEVs can be put on the road without
increasing the electricity demand during winter’s weekday evenings?
In the graph below showing electricity demand in France over one winter day, it appears that:
· Peak demand (84 000 MW around 6pm) is 32% higher than the lowest demand (63 400
MW at 4 am).
· The highest demand during off-peak hours (between midnight and 6am – about
72 700 MW), is about 20% lower than the peak demand.
· The energy available between midnight and 6am (striped zone) is about 91 000 MWh
(= (84 000 MW – 68 800 MW) x 6 h)
Source: http://www.sauvonsleclimat.org/new/spip/IMG/pdf/Acket-Nucleaire_et_suivi_reseau.pdf
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Assuming that 100% BEVs charge at night, starting at midnight (this can easily be done by
installing a timer on the plug connected to the BEV), and knowing that BEV loading current is
highest during the first hours of battery loading – and comparatively very low after 6 hours, then
about 20% of the peak power is available for BEV charging at night (between midnight and 6 am)
without exceeding the peak demand.
To simplify the computation, we assume that all BEVs will in the first stage be passenger cars, as
well as very small trucks, which draw similar power to electric cars, and neglect:
· Electric bicycles, scooters and motorcycles, which draw comparatively little power.
· Heavy trucks and busses, which are only likely to reach significant numbers in 5 to 10
years if ultra-fast-charging batteries become available.
Assuming that:
· Car-like BEVs drive on the average 50 km per weekday (this is probably a maximum),
· BEVs consume on the average 20 kWh per 100 km (realistic figure in urban traffic),
· BEVs draw on the average 10 Amps or 1.56 kW (= 10 A x 220 / SQRT (2)) during the first
6 charging hours (realistic figure).
Then each EV will charge 10 kWh per day and draw 10 Amps (2.2 kW) between midnight and 6
am.
In France, according to the above graph, the instantaneous power available between midnight and
5am without exceeding peak power is at least 11 300 MW (= 84 000 MW – 72 700 MW), and the
energy available during this time is about 91 000 MWh (see above). Considering:
· Instantaneous power: the maximum number of EVs that can charge without exceeding
peak power is 7.3 million (= 11 300 000 kW / 1.56 kW).
· Energy: the maximum number of EVs that can charge without exceeding energy available
between midnight and 6am is around 9.1 million (= 91 000 000 kWh / 10 kWh).
Taking the most conservative of these two figures, we conclude that, under our assumptions, the
electrical power infrastructure will not have to be reinforced before the total number of BEVs in
France reaches 7.3 million.
NOTES:
·
This computation assumes that all BEVs are electric cars (and ultra-small trucks). It ignores
electrical bicycles and scooters whose numbers are growing fast. It also ignores electrical
busses and trucks, which will need to charge in the daytime and are likely to reach
significant numbers in 5 to 10 years assuming ultra-fast-charging batteries become
available (which is likely). If we were to take these additional BEVs into account, our
numbers would be slightly lower.
·
All other assumptions are rather conservative. Notably we assume that all BEVs will
charge at maximum power between and only between midnight and 6am. However it is
also possible to charge many more BEVs at other hours (except the peak hour) without
exceeding the peak hour’s maximum.
·
Smart electrical power metering will become compulsory between 2020 (80%) and 2022
(100%). This will offer consumers the possibility and price incentives to charge only off
peak hours and will therefore increase the number of BEVs that can be put on the road
without requiring additional electrical infrastructure.
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·
The 7.3 million number is high compared to the current number of BEVs in France,
estimated to 11 000 in 2007 by IEA – mostly bicycles and scooters. There is a lot of room
for development!
·
Knowing that there are about 32 million cars in France (for a population of about 65
million) (source: http://www.statistiques-mondiales.com/ue_voitures.htm), it means that
nearly one car out of four (23%) can be a BEV without requiring additional electrical
infrastructure.
·
Assuming that the French figures can be extrapolated to the whole of Europe, and
considering that there are about 175 million cars in Europe, it would then be possible to put
40 million BEVs (= 175 million x 23%) on the European roads without requiring additional
electrical infrastructure.
·
Assuming that in France, 4 million cars belong to a two-car family (realistic estimate), all
second cars could be BEVs without additional infrastructure. It would therefore be an
excellent idea to provide strong incentives to promote BEVs as second car (such as an
additional tax on the second fossil fuel car): the BEV would be small, light and low-power,
and used for daily commuting and short trips, while the fuel car would be used for weekend trips and holidays, which represent only a small percentage of the mileage, and could
therefore be a big and powerful family car without causing overall too much emissions.
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Sources
Whenever possible, we have used reliable sources for the parameters used in this study and cited
the sources for the parameters which originate from a single source.
However, in several cases, different authoritative sources give different values for the same
parameter. In this case, we have consulted experts and/or used our own judgement to estimate an
adequate value for these parameters. In order to simplify the text, we have then omitted to cite all
these sources.
Status
This draft has been peer-reviewed by two experts:
· Professor Joeri Van Mierlo, VUB
· Yves MARENNE, Responsable Equipe Bilan ICEDD
Their corrections and comments have been integrated in this final draft, which is currently
proposed to the reviewer for final comments and/or acceptation.
Also, we intend to detail and further justify chapter 7’s conclusions in a later release.
If you wish to receive subsequent releases, kindly consult http://www.goingelectric.org/what/reports.htm where the latest version will systematically be posted, or let us know
by email at 2008@going-electric.org.
Copyright © European Association for Battery Electric Vehicles, 2008. All rights reserved.
Distribution and reproduction are welcomed on condition that the source and the URL of the
association’s website are cited: www.going-electric.org.
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